(1) Field of the Invention
The present invention relates generally to laminated wood products, and in particular to construction materials, such as flooring and the like manufactured from a plurality of wood segments bonded together in the horizontal or vertical dimension, or both, to form a single piece.
(2) Description of the Prior Art
A wood of increasing significance in the manufacture of building components, such as flooring, as well as furniture parts, is obtained by recycling beams and other framing lumber from commercial, residential and industrial buildings constructed in the late 1800s and early 1900s. Most of the reclaimed wood is long leaf or loblolly southern yellow pine, the heartwood of which is known as heart pine, which is of great beauty, with a distinctive grain pattern and a rich patina. Other woods, such as red and white oak, Douglas fir, redwood, bald cypress, chestnut, maple, hemlock, spruce, and others are also being reclaimed.
Due to its limited availability, and the cost of reclaiming and processing, this wood tends to be relatively expensive when compared to new lumber. Moreover, the dimensions of the pieces that can be cut from the reclaimed beams and other original lumber pieces, is often less than the dimensions desired in the pieces used in building or furniture construction. For example, flooring manufactured from reclaimed lumber often produces narrow widths, although wider boards are often desired for aesthetics. A similar problem is incurred in the manufacture of flooring and other wood components from newly cut trees.
In order to meet the demand for wider, longer and/or thicker wood pieces, and reduce the cost, strips of wood are often glued together or to non-wood substrates to increase the width, thickness and/or length of the wood piece. That is, two relatively narrow strips can be edge bonded to form a composite wood piece that has the width of the combined strips. The bottom face of a relatively thin layer or ply of the more costly wood can also be laminated to the upper face of a substrate to produce a thicker, but less costly wood piece. Two relatively short pieces can be glued end-to-end to produce a longer piece.
In addition to reducing the cost of the wood piece, proper face lamination to form a thicker wood piece has the advantage of imparting greater stability to the piece. Face laminated pieces are generally formed of an odd number of layers or plies, with alternating plies laid transverse to each other. For example, in a three ply laminate, the upper surface ply and the backing ply will have their grain extending in a longitudinal direction, while the grain of the center ply will be transverse to the longitudinal direction. The surface and backing plies will also be "balanced" in a known manner to equalize their tendency to cup or warp, taking into account the particular characteristics of wood types and thickness.
While prior art laminated wood products have considerable utility, further improvements are needed in order to improve the appearance and usefulness of this material. Two significant problems are addressed by the present invention. One improvement relates to improvements in the appearance of edge bonded wood laminates, while the other improvement relates to face bonded wood laminates. These improvements may be used alone or in combination in the production of improved laminated wood products.
As noted, edge bonded wood laminates are manufactured by bonding, e.g., gluing, two or more wood strips to each other at their abutting edges to form a larger composite wood piece having the desired width. The resultant composite product has physical properties much like those of a single wood piece. However, due to the differences in the color and grain of the individual boards, the resultant composite board still has the appearance of plural boards, and not that of a single board.
One attempt to improve the appearance of laminated wood boards, and simulate the appearance of a single board, is described in U.S. Pat. No. 5,135,597 to Barker. A product formed in accordance with the Barker teaching is manufactured by cutting adjacent wood strips from a larger lumber piece, and then alternately rotating the pieces in opposite directions about their longitudinal axes. Edges facing toward each other after rotation are then edge glued.
It is still readily apparent that the boards manufactured by the Barker procedure are made from two or more individual pieces, due primarily to the difference in light reflectance of the individual pieces, and the juxtaposition of knots and other character markings. Thus, there is still a need for an improved composite, edge bonded, wood laminate visually more similar to a single wood piece.
A second problem exists with face bonded wood laminates, particularly laminates with dimensioned edges used to join two or more laminate pieces or strips together at their edges to cover a large surface area. A common example of this type of product is wood flooring formed of a surface ply of relative more costly wood that has an upper exposed surface, a backing ply, and a transversely oriented intermediate layer of a relatively inexpensive wood.
The grain of the flooring strip surface and backing plies is normally in the direction of the longer dimension of the strip, with the grain of the intermediate ply being transverse to the longer dimension, providing dimensional stability to the piece.
The edges of each flooring strip are normally dimensioned by cutting a groove into one edge and one end of the piece, and a tongue in the opposed edge and end. Thus, when two of the pieces are joined at their edges, the tongue along the edge of one piece fits into the groove along the edge of another piece. Similarly, the tongue at the end fits into the groove of an abutting piece.
Since the grain of the intermediate ply is transverse to the lumber dimension, there is a tendency for the short tongue piece at the end of the strip to break off under the stresses experienced at the ends of abutting flooring. Therefore, it is the industry practice to bond a shim of multilayer plywood or some other type of very strong material between the face and backing layers at the end of the piece and form the tongue from this shim. While effective, the cost of the product is increased and the appearance is undesirable. A face laminated structure eliminating the need for this shim would be much preferred.